1. Technical Field
The present invention relates to a Fresnel lens sheet holding structure and a rear projection display. More specifically, the present invention relates to a Fresnel lens sheet holding structure capable of holding a thin Fresnel lens sheet in a satisfactorily plane shape, and a rear projection display provided with the Fresnel lens sheet holding structure.
2. Background Art
FIG. 24 shows a rear projection display 101 by way of example. The rear projection display 101 projects imaging light 102 obliquely on a screen 103. FIG. 26 shows a Fresnel lens sheet 111 proposed in Patent document 1 to be employed in the rear projection display 101. The Fresnel lens sheet 111 is provided with total-reflection Fresnel lens elements 112 arranged on its entrance surface. Each of the Fresnel lens elements 112 is a prism 112 having a triangular cross section. The prism 112 has an entrance facet 113, and a total-reflection facet 114 that reflects all or part of light 102 fallen on the entrance facet 113 in a total-reflection mode to deflect the light 102 in a desired direction.
The total-reflection Fresnel lens sheet is formed by applying a molding resin to a flat forming mold 7, curing the molding resin applied to the forming mold 7 to form the Fresnel lens sheet 1, and releasing the Fresnel lens sheet 1 from the forming mold 7. Since the Fresnel lens elements 2 are engaged with the forming mold 7, it is difficult to release the Fresnel lens sheet 1 from the forming mold 7 when the Fresnel lens sheet 1 is thick because the thick Fresnel lens sheet 1 is has low flexibility. Therefore, the Fresnel lens sheet 1 is formed in a thickness of 3 mm or below to achieve mold releasing work efficiently.
References cited
Patent document 1: JP 61-208041 A
Patent document 2: JP 4-249235 A
Patent document 3: JP 4-256941 A